Just a small footnote to this great thread, I use LCI / specter water cans. They are not cheap (thought sometimes you can find a great deal on them used) but they are mil spec and seemingly indestructible. I think you can drive a car over one without damage.
They make both 2.5 and 5 gallon versions and a few different colors like tan, blue, black, green.
They are not cost-effective and don't replace a huge water tank, but they easy to move.
I suggest you get at least 1 silver coin. If you connect it to the negative lead on your power you can use any conductive material for the positive electrode. If you put a pinch of salt in a cup of water and your coin hooked to 3 or more volts into the water (and the other electrode) the white stuff you see descending is silver chloride which kills bacteria. In the absence of antibiotics you need something for wounds and infections, even illness. Silver even kills antibiotic resistant staph.
Last year my Britta water pitcher cracked, and was about to get a other one. Then I decided to study a better filter, and maybe cheaper. I stumbled on this larger gravity filter, like britta, but much more heavy duty. It's not portable, so it uses a spout instead of pouring. Berkey filters, found on amazon from 200 to about 500 each. While it costs much more than a britta, it tastes much better and filters WAY more tolerance than any other filter I found, even filtering radioactive stuff. Though costly at first, it filters around 3000 gallons (if i remember correctly) before needing a filter change. If I drink 2 gallons a day, it'd take 1500 days before refill, and I have a backup filter, so 6000 gallons I can treat.
For emergency, i do have a 120 gallon aquarium IF I NEEDED it haha. I do have 5 gallons bottles stored in the garage, and a army of 1 gallons tucked throughout the house and even 2 in my car.
best tasting water I've had.
You need to be careful drinking DeIonized or Distilled water. Because it lacks ANY dissolved chemicals it will leach chemicals OUT of your body. If you cook with it you will be fine because you are adding plenty of goodies in. Even Tea or Coffee is good. But if you count on this as your drinking water then you should add minerals. It is easy to do, just add sea salt, about a quarter teaspoon per quart. You will hardly notice any taste.
However there is a new danger to think about with sea salt. Any sea salt extracted from the Pacific Ocean is out due to Fukashima Japan's nuclear release problem. Add to this that any sea salt extracted from ANY ocean today is going to include the pollution that we, humankind, have been adding to the oceans for the last hundred years or so. This is especially true for the mediterranean sea since it is kind of land locked and we, humankind, have been polluting it for almost 2000 years. Granted that was mostly just sewage until 100 years ago when we got more serious about it.
So that leaves us with the ancient deposits such the Great Salt Lake, Utah, and the Himalayan deposits (India, Tibet, Pakistan... ). There are some other underground, protected deposits such as under Detroit and Chicago but these are usually purified before reaching market to just sodium chloride with a little added Iodine.
The blood that flows through our veins is almost chemically identical to sea water with the main difference being that our blood is composed of various organized structures, red blood cells, white blood cells, etc.
So yes, sea salt contains all of the essential minerals and in just the right ratios.
I feel like a big obvious first step in a crisis like this is to fill the tub. Yes, you'll run out. But as a first reaction to a big crash, filling the tub will get you a few days of water now. This should be on the 'FIRST' list.
Of course, if you have a storage plan, even better. But vacuum sealed rice, flour, and sugar...as well as a source of filtered water...you are only missing firearms.